Hollow article and its manufacturing method and apparatus thereof

ABSTRACT

The present invention is a hollow article with an integral impact absorbing rib and the method of manufacturing the same. The apparatus is a hollow article made of thermoplastic resin and integrally formed by blow molding, comprising a first wall and a second wall confronting across a spacing. There is an integral rib between the first wall and the second wall, wherein the integral rib comprises a flat rib between the walls and one or more hollow ribs adjacent to each of two side ends of the flat rib. The impact absorbing rib is disposed at intervals and in an impact action direction. The rib is uniform in shape, dimensions and wall width, and free from reduction of wall width of the inner rib, yet possessing proper structural support and mechanical strength, and excellent in impact absorbing performance.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional application that is related andclaims priority under 35 U.S.C. § 120 to co-pending U.S. Non-ProvisionalApplication No. 09/794,579 which is incorporated herein by reference forall purposes, and which in turn claims priority under 35 U.S.C. Section119 from a Japanese Patent Application No. 2000-54898 filed on Feb. 29,2000, and a Japanese Patent Application No. 2000-394056 filed on Dec.26, 2000, which are incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

[0002] 1. Technical Field of the Invention

[0003] The present invention relates to thermoplastic hollow articlesthat are excellent in rigidity and impact absorption qualities, as wellas to the manufacturing process for producing the hollow articles.

[0004] 2. Background Art

[0005] Hollow articles are well known in the art and used in a varietyof industries and applications. These plastic hollow articles arelightweight, strong, and relatively inexpensive to manufacture usinginjection or blow molding techniques.

[0006] There are numerous examples of products that employ hollowarticles, such as ducts, panels, or housings for electronics,appliances, automobiles, and house wares. In many homes these hollowarticles are found in walls, partitions, and panels, such as entrancedoors, and indoor air conditioning ducts. Furniture is also manufacturedwith hollow structures, and includes top plates of desk, partitionpanels, and bookshelf panels.

[0007] In the appliance sector, housings of some of the components arehollow such as used for refrigerators and televisions. The hollowarticles are also used in office equipment, such as the housings of copymachines, facsimile machines and computer peripherals.

[0008] Panels and ducts of dwelling facilities, furniture panel, housingof electric household appliances, housing of office equipment andautomotive parts are often required to have a high rigidity. Hollowarticles used in such applications are manufactured in integralstructures combining a first wall and a second wall by means of a riblinking them mutually within a hollow space. In cases where theappearance is important on both face and back surfaces, a structuretermed an “inner rib” is employed. Thus, the first wall and the secondwall are projected, in blow molding, until a part of the second wallcontacts with a wall to be linked integrally within the hollow spacethere between.

[0009] The automobile industry uses hollow articles because of themechanical properties and weight characteristics. Automotive partsinclude console box lid, hood, door panel, and air conditioning duct.For example, in order to assure the rigidity as a product or to protectthe crew from impact of collision, an automotive roof side duct isdisposed near both sides of ceiling as explained in Japanese PatentApplication Laid-Open No. 2000-43541.

[0010] The automobile industry is particularly interested in increasingthe safety of the vehicles, and at a minimum, complying with the certainsafety guidelines. According to the Federal Motor Vehicle SafetyStandards (FMVSS), the hollow articles must have a minimum level ofimpact absorption. The guidelines are established under the Departmentof Transportation by the National Highway Traffic Safety Administration.There are a number of guidelines and requirements, including FMVSS 201that addresses occupant protection in interior impact. There are otherguidelines that describe related topics such as resistance to roofcrushing. Head injuries are calculated according to a ‘heading injurycriteria’ (HIC) that is obtained from the deceleration of the headduring the duration of the impact. These federal standards must besatisfied in order for vehicle to enter the U.S. market. And, theseregulations are continuously being updated as new innovations andfeatures result in improved safety characteristics.

[0011] There are many studies that demonstrate that significant headinjuries and trauma occur when the driver or passengers head strikes theinterior roof and side panels. A rigid interior wall offers littleimpact absorbing qualities when struck by a human head. There are anumber of techniques used to impart some shock absorbing qualities intothe roof and interior panels, but the strict government standardscontinue to increase and demand greater safety thresholds. The use ofceiling air bags and structural modifications to the support elementsare designed to address the impact absorbing qualities, however thereare issues such as cost and manufacturability that limit the wide-spreaduse of such features.

[0012] As shown in prior art FIG. 11, the inner rib of a roof side ductis integrally formed by blow molding, wherein an inside wall 101 facinga ceiling interior member 107 and an outside wall 102 facing an innerpanel 106 of car body confront each other. A flat impact absorbing rib103 is disposed along the longitudinal direction in a space 110 betweenthe inside wall 101 and outside wall 102. A general manufacturing methodof this roof side duct is explained by referring to FIG. 12a, 12 b, andFIG. 13.

[0013] Prior art FIG. 12a shows a molten parison 300 being poured intoopened split molds 201, 202, and then the molds are closed. Next, a ribforming plate 203 is projected toward the second mold 202, and a neck303 is formed in the area of first wall 301 of the parison, and itsleading end is pressed tightly to the area of second wall 302. Then, asshown in FIG. 12a, the rib forming plate 203 is pulled in, thepressurized air is introduced into the parison 300, and is inflated intoa shape along the cavity by the internal pressure of the pressurizedair, and the neck 303 is pressed and deformed in the direction of thearrows, while confronting walls are fused integrally, so that an impactabsorbing rib 304 is formed.

[0014] According to the prior art, as shown in FIG. 13, when pulling inthe rib forming plate 203, after projecting the rib forming plate andforming a neck at first wall side of the parison, the neck is dragged inthe backward direction of the rib forming plate 203, or is elongated bythe blow pressure in the blow process, and the wall thickness and widthof the flat rib formed as the confronting walls of the neck arecompressed from both sides by internal pressure of the pressurized airare decreased. Thus, at portion 305 the inner rib is reduced in wallwidth and the shape, and the dimensions and wall thickness of the flatrib are not uniform on the whole. As a result, the rigidity and othermechanical strength of the impact absorbing rib 304 are lowered, and theduct having sufficient impact absorbing performance is lessened.Furthermore, the varying thickness of the inner rib results in someinconsistency in impact absorbing qualities. In the describedapplication, such a product may result in inadequate protection in theevent of a collision. Other applications may result in improper rigidityand strength and at the very least, inconsistency in the produced hollowarticle.

[0015] What is needed is a hollow article with a rib of uniform shape,dimensions and wall width. The rib should have excellent mechanicalstrength and properties. In one embodiment, such as automotive, thehollow article with the rib should have impact absorbing qualities toprotect the driver and passengers. The manufacturing method for such animproved hollow article should be cost-effective and have a low defectrate.

SUMMARY OF THE INVENTION

[0016] The invention is devised in the light of the problems of theprior art described herein. The present invention is a hollow articlehaving an impact absorbing rib uniform in shape, dimensions and wallwidth on the whole, especially free from reduction of wall width of theinner rib, yet possessing proper rigidity and mechanical strength, andexcellent impact absorbing performance.

[0017] Another aspect of the invention is to ensure compliance with theFMVSS 201 regulations addressing interior head injury criteria.According to FMVSS 201, the interior of the vehicle in the U.Smarketplace must have a head injury criteria (HIC) of less than 1000.The value is determined by striking a dummy head of a certain mass intothe regions of the vehicle interior at a certain speed and measuring theshock value. The present invention results in an article that is wellwithin the federal guidelines. In addition, present invention has agreater consistency and repeatability as compared to prior art productsthat have a higher rate of failure of compliance. The prior artcomponents are generally unable to satisfy the HIC standards, andtherefore cannot pass the FMVSS 201 specifications. For example, theroof side ducts of the prior art were tested and the HIC was found to beapproximately 1500, which is above the 1000 HIC threshold.

[0018] One object of the invention is a hollow article made of athermoplastic resin and integrally formed by blow molding, comprising afirst wall and a second wall confronting across a spacing, an integralrib between the first wall and the second wall, wherein the integral ribcomprises a flat rib projecting from the second wall to the first wall,and a hollow rib adjacent to each of two side ends of the flat rib,wherein the flat rib and the hollow rib are fused to an inner side ofthe first wall.

[0019] A further object is the hollow article, wherein the hollow rib istapered with a more narrow portion at the first wall. Additionally,wherein the integral rib is disposed along a longitudinal direction ofthe hollow article. And, wherein a plurality of the integral ribs aredisposed at a mutual spacing.

[0020] An additional object is the hollow article, wherein the integralrib is disposed in an impact action direction. Also, wherein the hollowarticle is an automobile component

[0021] An object of the invention is a hollow article made ofthermoplastic resin, integrally formed by blow molding, comprising afirst wall and a second wall confronting across a spacing, an integralrib disposed between the first wall and the second wall, wherein theintegral rib comprises a first flat rib projecting from the first wallto a fusion portion, a first hollow rib adjacent to each of two sideends of the first flat rib, a second flat rib projecting from the secondwall to the fusion portion, a second hollow rib adjacent to each of twoside ends of the second flat rib, wherein the first flat rib and thesecond flat rib are fused to each other at the fusion portion, andwherein the first hollow rib and the second hollow rib are fused to eachother at the fusion portion.

[0022] Another object is the hollow article, wherein the first hollowrib and the second hollow rib form a combined concave hollow rib. Also,the hollow article, wherein the integral rib is disposed along alongitudinal direction of the hollow article. Additional objects of theinvention include the hollow article, wherein a plurality of theintegral ribs are disposed at a mutual spacing, and also wherein theintegral rib is disposed in an impact action direction.

[0023] An object of the invention is a method of blow molding a hollowarticle having a first wall and a second wall confronting across aspacing, with an integral rib disposed between the first wall and thesecond wall, comprising the steps of opening a split mold, wherein thesplit mold has a first mold half with a cavity, a slide core and a pairof support cores on either side of the slide core, and a second moldhalf with a cavity, a slide core and a pair of support cores on eitherside of the slide core. Extruding a parison of molten thermoplasticresin between the split mold and closing the split mold, therebydeforming the parison with each sliding core and each of the pair ofsupport cores and forming a first recess and a second recess, wherein aleading end of the first recess and a leading end of the second recessare fused. Next, retracting each of the slide cores and introducing apressure substance into the parison and inflating the parison along acavity surface of the split molds and the support cores and forming theintegral rib between the first wall and the second wall, wherein theintegral rib comprises a pair of flat ribs and a pair of hollow ribs,and cooling the split mold, opening the split mold and removing thehollow article.

[0024] And additional object is the method of blow molding, wherein thestep of retracting the slide cores is simultaneous with the step ofintroducing the pressure substance. Also, wherein the pressurizedsubstance is a gas.

[0025] An object of the invention is a method of blow molding a hollowarticle having a first wall and a second wall confronting across aspacing, with an integral rib disposed between the first wall and thesecond wall, comprising the steps of opening a split mold, wherein thesplit mold has a first mold half with a cavity, and a second mold halfwith a cavity, a slide core and a pair of support cores on either sideof the slide core, extruding a parison of molten thermoplastic resinbetween the split mold, closing the split mold, deforming the parisonwith the sliding core and the pair of support cores and forming arecess, wherein a leading end of the recess is fused to an inner surfaceof an opposing wall side. Finally, retracting the slide core,introducing a pressure substance into the parison, inflating the parisonalong a cavity surface of the split molds and the support cores andforming the integral rib between the first wall and the second wall,wherein the integral rib comprises a flat rib and a pair of hollow ribs,cooling the split mold, opening the split mold and removing the hollowarticle.

[0026] A further object is the blow molding method, wherein the step ofretracting the slide cores is simultaneous with the step of introducingthe pressure substance. Furthermore, wherein the pressurized substanceis a gas.

[0027] An object of the invention is an apparatus for blow molding ahollow article from a thermoplastic resin, having a first wall and asecond wall confronting across a hollow space, and an integral ribdisposed for providing structural support and absorbing impact betweenthe first wall and the second wall, comprising a split mold with a firstmold half and a second mold half, a slidably engageable slide core forforming a flat rib disposed in at least one of the mold halves, a pairof support cores disposed on at least one of the mold halves for forminga hollow rib and adjacent to each of two side ends of the slide core,and a means of retracting the sliding core.

[0028] Additionally, the apparatus for blow molding, wherein the pair ofsupport cores is integrally disposed in the mold halves. And, whereinthe pair of support cores is retractable from within the mold halves.Finally, the apparatus for blow molding wherein a surface of the slidecore is treated with fluorine film coating so as to slide smoothly withthe parison.

[0029] Still other objects and advantages of the present invention willbecome readily apparent to those skilled in this art from the followingdetailed description, wherein I have shown and described only apreferred embodiment of the invention, simply by way of illustration ofthe best mode contemplated by me on carrying out my invention. As willbe realized, the invention is capable of other and differentembodiments, and its several details are capable of modifications invarious obvious respects, all without departing from the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings,wherein like reference numerals designate like structural elements, andin which:

[0031]FIG. 1a shows a hollow article for an automobile according to afirst embodiment of the invention, in which A is a schematic partialperspective view broken in the portion of impact absorbing rib

[0032]FIG. 1b shows a hollow article for an automobile according to afirst embodiment of the invention showing a schematic partial sectionalview along line A-A in FIG. 1a

[0033]FIG. 2a shows a hollow article for an automobile according to asecond embodiment of the invention, showing a schematic partialperspective view broken in the portion of impact absorbing rib

[0034]FIG. 2b shows a hollow article for an automobile according to asecond embodiment of the invention, showing a schematic partialsectional view along line A-A in FIG. 2a

[0035]FIG. 3 is an explanatory diagram showing an example of use of thehollow article for an automobile

[0036]FIG. 4a is an example of a manufacturing method of the hollowarticle for an automobile, with an explanatory diagram showing a stateof disposing a parison between opened molds

[0037]FIG. 4b is an example of a manufacturing method for the hollowarticle for an automobile, showing a schematic sectional view along lineA-A in FIG. 4a.

[0038]FIG. 5a shows a completely closed state of the molds after theprocess shown in FIG. 4a, illustrating a schematic partial sectionalview along the axial direction of parison

[0039]FIG. 5b shows a completely closed state of the molds after theprocess shown in FIG. 4a, illustrating a schematic sectional view alongline A-A in FIG. 5a

[0040]FIG. 6a shows a completely withdrawn state of the slide core afterthe process shown in FIG. 5a, depicting a schematic partial sectionalview along the axial direction of parison

[0041]FIG. 6b shows a completely withdrawn state of the slide core afterthe process shown in FIG. 5a, depicting a schematic sectional view alongline A-A in FIG. 6a

[0042]FIG. 7a shows a completely introduced state of the pressurized airafter the process shown in FIG. 6a, showing a schematic partialsectional view along the axial direction of parison

[0043]FIG. 7b shows a completely introduced state of the pressurized airafter the process shown in FIG. 6a, showing a schematic sectional viewalong line A-A in FIG. 7a

[0044]FIG. 8a is another example of a manufacturing method of a hollowarticle for the automobile, depicting an explanatory diagram showing astate of disposing a parison between opened molds

[0045]FIG. 8b is another example of a manufacturing method of a hollowarticle for the automobile, depicting a schematic sectional view alongline A-A in FIG. 8a.

[0046]FIG. 9a shows a completely closed state of the molds after theprocess shown in FIG. 8a, illustrating a schematic partial sectionalview along the axial direction of parison

[0047]FIG. 9b shows a completely closed state of the molds after theprocess shown in FIG. 8a, illustrating a schematic sectional view alongline A-A in FIG. 9a

[0048]FIG. 10a shows a completely introduced state of the pressurizedair after the process shown in FIG. 9a, showing a schematic partialsectional view along the axial direction of parison FIG. 10b shows acompletely introduced state of the pressurized air after the processshown in FIG. 9a, showing a schematic sectional view along line A-A

[0049]FIG. 11 is a prior art schematic sectional view after installationof an inner panel, showing a conventional roof side duct.

[0050]FIG. 12a is a prior art process for manufacturing the roof sideduct shown in FIG. 11, depicting a schematic sectional view showing aforming state with the narrow neck in the parison by the rib formingplate

[0051]FIG. 12b is a prior art process for manufacturing the roof sideduct shown in FIG. 11a, depicting a schematic sectional view showing astate upon completion of the introduction of pressurized air

[0052]FIG. 13 is a prior art schematic sectional view along line X-X inFIG. 12b

[0053]FIG. 14 is a sectional view side view showing shape of the hollowrib for the embodiment using two sliding cores, wherein the combinedhollow ribs are concave in appearance

[0054]FIG. 15 is a sectional view side view shape of the hollow rib forthe embodiment using one sliding core, wherein the hollow rib is taperedin appearance

REFERENCE NUMERALS

[0055]FIGS. 1a, 1 b, 14

[0056]1 Hollow matter for automobile

[0057]2 First wall

[0058]3 Second wall

[0059]4 First side wall

[0060]5 Second side wall

[0061]6 First flat rib

[0062]7 Second flat rib

[0063]8 First hollow rib

[0064]9 Second hollow rib

[0065]10 Impact absorbing rib

[0066]11 Fusion portion

[0067]FIGS. 2a, 2 b, 15

[0068]21 Hollow matter for automobile

[0069]22 First wall

[0070]23 Second wall

[0071]26 Flat rib

[0072]27 Hollow rib

[0073]30 Impact absorbing rib

[0074]31 Fusion portion

[0075]FIG. 3

[0076]2 First wall

[0077]3 Second wall

[0078]4 First side wall

[0079]5 Second side wall

[0080]35 Connection duct

[0081]35 a, 35 b Junction

[0082]36 Discharge port

[0083]FIGS. 4a, 4 b

[0084]41 First mold

[0085]41 a, 42 b Cavity

[0086]42 Second mold

[0087]43 Extrusion head

[0088]44 Parison

[0089]45, 47 Slide core

[0090]46, 48 Support core

[0091]FIGS. 5a, 5 b

[0092]44 a First recess

[0093]44 b Second recess

[0094]51 Fusion portion

[0095]FIG. 6

[0096]44 Parison

[0097]FIGS. 7a, 7 b

[0098]1 Hollow matter for automobile

[0099]2 First wall

[0100]3 Second wall

[0101]6 First flat rib

[0102]7 Second flat rib

[0103]8 First hollow rib

[0104]9 Second hollow rib

[0105]51 Fusion portion

[0106]FIGS. 8a, 8 b

[0107]61 First mold

[0108]62 Second mold

[0109]63 Extrusion head

[0110]64 Parison

[0111]65 Slide core

[0112]FIGS. 9a, 9 b

[0113]64 Parison

[0114]64 a Recess

[0115]65 Slide core

[0116]66 Support core

[0117]71 Fusion portion

[0118]FIGS. 10a, 10 b

[0119]22 First wall

[0120]23 Second wall

[0121]24 First side wall

[0122]25 Second side wall

[0123]26 Flat rib

[0124]31 Fusion portion

[0125]61 First mold

[0126]61 a Cavity

[0127]62 Second mold

[0128]65 Slide core

[0129]66 Support core

[0130]FIG. 11

[0131]101 Inside wall

[0132]102 Outside wall

[0133]103 Impact absorbing rib

[0134]106 Inner panel

[0135]107 Ceiling interior member

[0136]110 Space

[0137]FIGS. 12a, 12 b

[0138]201 Split mold

[0139]202 Split mold

[0140]203 Rib forming plate

[0141]300 Parison

[0142]301 Support core

[0143]302 Second wall

[0144]303 Neck

[0145]304 Impact absorbing rib

[0146]FIG. 13

[0147]304 Impact absorbing rib

[0148]305 Reduced portion

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0149] A first embodiment of the hollow article of the presentinvention, typically used in the automobile industry, is described indetail herein. FIG. 1a shows the hollow article as a partial perspectiveview broken in the portion of impact absorbing rib. FIG. 1b is a partialsectional view along line A-A in FIG. 1a.

[0150] The hollow article 1 of FIG. 1a is made of thermoplastic resinthat is integrally formed by blow molding. It includes a first wall 2and a second wall 3 mutually confronting across a space in an impactacting direction. The impact absorbing direction refers to theorientation of the hollow article in the desired application. Forexample, if the hollow article 1 were deployed in a roof of anautomobile, either the first or second wall 2, 3 would be facing theinterior of the vehicle and subject to being struck by the head ofdriver and/or passengers.

[0151] In this particular described embodiment the first wall 2 andsecond wall 3 are inclined with respect to each other. There is a firstside wall 4 and a second side wall 5 formed consecutively to both sideends of the first wall 2 and second wall 3 confronting nearly parallelto each other.

[0152] The sectional shape of the hollow article 1 is not limited to thetrapezoidal shape as shown in the embodiment of FIG. 1a with respect tothe mutually confronting first wall 2 and second wall 3 being inclined.The article 1 may be formed as a square, rectangle, parallelogram orother arbitrary shape depending on the application and still be withinthe scope of the present invention.

[0153] Between the first wall 2 and second wall 3, there is an impactabsorbing rib 10 formed integrally by blow molding. This impactabsorbing rib 10 includes a first flat rib 6 projecting from the firstwall 2 with a first hollow rib 8 adjacent to both side ends of the firstflat rib 6. A second flat rib 7 projects from the second wall 3 with asecond hollow rib 9 adjacent to both side ends of the second flat rib 7.The first and second flat rib 6, 7 meet at the fusion portion 11 as dothe first and second hollow rib 8, 9. In a preferred embodiment the flatrib 6, 7 is generally rectangular with side ends connected to the hollowribs 8, 9.

[0154] In the embodiment shown in FIG. 14, the shape of theinterconnected first and second hollow ribs 8, 9 is concave. The concaveappearance is a result of the mating of the first hollow rib 8 and thesecond hollow rib 9 at the fusion portion 11. The first hollow rib 8 andsecond hollow rib 9 are both tapered such that they are more narrow atthe fusion portion 11, resulting in a concave structure in oneembodiment of the invention. The tapered appearance of the first andsecond hollow rib 8, 9 is affected by the shape of the support core tosome extent. Thus, in one of the embodiments, a tapered support corewith a narrow portion extending to the fusion portion affects the shapeof the hollow rib. However, the present invention is not limited to aconcave shape for the hollow rib 8, 9.

[0155] A second embodiment of a hollow article 21, also useful in theautomobile industry is described and depicted in FIGS. 2a and 2 b. FIG.2a shows a hollow article 21 according to the second embodiment, aschematic partial perspective view broken in the portion of impactabsorbing rib. FIG. 2b is a schematic partial sectional view along lineA-A in FIG. 2a.

[0156] A hollow article 21 is made of thermoplastic resin formedintegrally by blow molding, and includes first wall 22 and second wall23 mutually confronting across a space in an impact acting direction.The second wall 23 is inclined to the first wall 22 in this embodiment.A first sidewall 24 and second sidewall 25 are formed consecutively toboth side ends of the first wall 22 and second wall 23 respectively andconfront nearly parallel to each other.

[0157] Between the first wall 22 and second wall 23, there is an impactabsorbing rib 30 formed integrally by blow molding. This impactabsorbing rib 30 includes a flat rib 26 projecting from second wall 23to first wall 22 and a hollow rib 27 adjacent to both side ends of theflat rib 26 which are integrated through a fusion portion 31.

[0158] As shown in FIG. 15, the shape of the impact absorbing rib 30 istapered. The tapered appearance is a result of the mating of the hollowrib 27 to the fusion portion 31. The hollow rib 27 is both tapered suchthat it is more narrow at the fusion portion 31. However, the presentinvention is not limited to a tapered shape for the impact absorbing rib30.

[0159] The thermoplastic resin used for blow molding the hollow articleis not particularly limited, and any of the thermoplastic gradematerials are acceptable. Various compounds may be used for the presentinvention, and preferred examples include high-density polyethylene,medium density polyethylene, polypropylene, denatured polyphenyleneoxide, polycarbonate, polyamide, and ABS resin.

[0160] The hollow article of the present invention may be used inautomobile applications, such as for automobile damper, hood, door,console box lid, air conditioning duct, and other interior and exteriorparts. The implementation of the present invention in the automotiveindustry can enhance the safety of the vehicle and provide betterprotection for the driver and passengers.

[0161] The head injury criteria obtained by the present invention wasapproximately 800, which is within the guidelines established by FMVSS201. Prior art hollow articles tested had a head injury criteria thatwas above the limit set by FMVSS 201. In addition, one of the advantagesof the present invention is the repeatability, reliability andconsistency of the hollow articles. Prior art articles tend to have amuch greater variability in the thickness and dimensions of the impactabsorbing rib and effecting the head injury criteria.

[0162]FIG. 3 illustrates an example of the hollow article shown in FIG.1a in the air conditioning duct for an automobile, disposed at bothsides of the car compartment ceiling. As shown in FIG. 3, the hollowarticle 1 is disposed at both sides of the car compartment ceiling andshows two impact absorbing ribs 10 disposed at an interval along thelongitudinal direction of the compartment ceiling ducts. One end of theducts interconnect with junctions 35 a, 35 b which are disposed at bothsides of a connection duct 35 and the second end side of the duct isclosed. First wall 2 and second side wall 5 face the inside of thecompartment, and second wall 3 and first side wall 4 face the car bodyside, and a discharge port 36 is provided at a position not forming theimpact absorbing rib 10 of first wall 2.

[0163] The air conditioning air supplied from the air conditioner (notshown) through the connection duct 35 is discharged toward thepassengers and driver through a passage of the hollow article 1 formedat both sides of the impact absorbing rib 10, from the discharge port36, so that the compartment can be air conditioned uniformly.

[0164] In the event of a car crash, if the head of a driver or passengercollides against the first wall 2, this impact is absorbed by the impactabsorbing rib 10 lessening the effects or damages from the impact.

[0165] The impact absorbing rib 10 as described herein is not limited toa single rib per article. As shown in FIG. 3, two or more impactabsorbing ribs 10 may be disposed as required at a mutual spacing. Thedetermination of the mutual spacing depends upon many factors includingthe required structural support, length of the article, dimension of thearticle, compounds used to manufacture the article, as well the intendedimpact absorbing qualities desired.

[0166] An example of a manufacturing system of the hollow article isexplained in detail in FIGS. 4a and 4 b. This particular embodimentutilizes two sliding cores 45, 47. A first mold 41 and second mold 42are opened. In one embodiment the support cores 46, 48 and slide cores45, 47 are projecting to a position where the leading ends 45 a, 47 a ofthe sliding cores are nearly flush with leading ends 46 a, 48 a of thesupport cores 46, 48, and wherein the sliding core is a generallyrectangular flat plate disposed between the support cores.

[0167] The first mold 41 includes a cavity 41 a for defining the outersurface of nearly half of the first wall 2 side of tie hollow article,the slide core 45 for forming first flat rib 6, and a pair of supportcores 46 for forming first hollow rib 8 disposed adjacently to both sideends of first flat rib 6. By contrast, the second mold 42 includes acavity 42 a for defining the outer surface of the remaining portion ofthe second wall 3 side of the hollow article, the slide core 47 forforming second flat rib 7, and a pair of support cores 48 for formingsecond hollow rib 9 disposed adjacently to both side ends of second flatrib 7.

[0168] The support cores 46, 48 are not limited to the illustratedexample. Retractable support cores 66 like those shown in FIG. 8 may bealso used in the present invention.

[0169] Next, a parison 44 made of molten thermoplastic resin is extrudedfrom an extrusion head 43 of an extruder (not shown) and is poured intothe opened molds 41, 42, and then the molds 41, 42 are gradually closed.

[0170] As the molds 41, 42 are being closed, with or without a timedelay, the slide core 45 and support cores 46 of the first mold projecttowards the slide core 47 and support cores 48 of the second mold 42. Asthe molds are being closed, as shown in FIGS. 5a and 5 b, the first wallside of the parison 44 is pushed and deformed by the slide core 45 andsupport cores 46 of the first mold 41 and one recess 44 a is formed,while the second wall side of the parison 44 is pushed and deformed bythe slide core 47 and support cores 48 of the second mold 42 and secondrecess 44 b is formed. When the molds 41, 42 are completely closed, theleading end of first recess 44 a and leading end of second recess 44 bare fused, and a fusion portion 51 is formed.

[0171] Then the slide cores 45, 47 are retracted as shown in FIGS. 6aand 6 b. In this case, both sides of first recess 44 a and second recess44 b are fixed at their positions by the support cores 46, 48. Onlyslide cores 45, 47 are drawn back, and therefore as the slide cores 45,47 are retracted, the recesses 44 a, 44 b formed in the parison 44 arenot dragged. The combination of the elements contribute to the hollowrib being formed about the support cores with uniform and consistentstructural dimensions. Contributing to the production is the surfacetension of the thermoplastic material at the fusion portion to maintainthe shape within the molds 41, 42 while the sliding cores 45, 47 areretracted.

[0172] An inflation or blow means such as a blow needle (not shown) ispoked into the parison 44, and pressurized air is introduced to inflatethe parison 44 into a shape along the outer surface of the cavities 41a, 42 a and support cores 46, 48, and the wall surfaces facing therecesses 44 a, 44 b are pressed and deformed by internal pressure of thepressurized air, as shown in FIGS. 7a and 7 b. Although pressurized airis used in this embodiment, it is also within the scope of the inventionto utilize pressurized gases to inflate the parison 44.

[0173] As a result of the pressurized air, the first wall 2 and secondwall 3 are disposed in a confronting orientation. Between the first wall2 and second wall 3, the leading ends of the first flat rib 6 projectfrom the first wall 2. The first hollow rib 8, adjacent to both sideends of first flat rib 6, projects from the first wall 2. The leadingends of the second flat rib 7 project from second wall 3. The secondhollow rib 9, adjacent to both side ends of second flat rib 7, projectsfrom the second wall 3. The first flat rib 6 and second flat rib 7 areintegrated through the fusion portion 11, thereby completing impactabsorbing rib 10.

[0174] After cooling in the molds 41, 42, and opening the molds, thehollow article 1 is removed and deflashed.

[0175] Another example of a manufacturing method of the hollow articleof the present invention is explained herein. As shown in FIGS. 8a, 8 b,first mold 61 and second mold 62 are opened with the slide core 65 andsupport core 66 of the first mold 61 and second mold 62 retracted asshown.

[0176] Herein, the first mold 61 includes a cavity 61 a for defining theouter surface of nearly half of the first wall 22 side of the hollowarticle 21. By contrast, the second mold 62 includes a cavity 62 a fordefining the outer surface of the remaining portion of the second wall23 side of the hollow article 21, the slide core 65 for forming a flatrib 26, and a pair of support cores 66 for forming a pair of hollow ribs27 disposed adjacently to both side ends of the flat rib 26. In thisparticular embodiment the pair of support cores 66 are retractable. Thesupport cores 66 are not limited to the illustrated retractable example,but may be disposed integrally in the second mold 62.

[0177] A parison 64 made of molten thermoplastic resin is extruded froman extrusion head 63 of an extruder not shown in the diagram, and ispoured into the opened molds 61, 62, and the molds are closed.

[0178] As the molds 61, 62 are being closed, with or without a timedelay, the slide core 65 and support core 66 project toward the secondmold 66, as shown in FIGS. 9a and 9 b. The first wall side of theparison 64 is pushed and deformed and a recess 64 a is formed, then theleading end of the recess 64 a is fused to the inner surface of thesecond wall side of the parison, and a fusion portion 71 is formed.

[0179] After closing the molds 61, 62, while the support core 66 isprojecting, the slide core 65 is retracted. As the slide core 65 isretracted, the recess 64 a formed in the parison 64 is not dragged orotherwise deformed.

[0180] Next, blow means, such as a blow needle (not shown), is pokedinto the parison 64, and pressurized air is introduced to inflate theparison 64, as shown in FIGS. 10a and 10 b into a shape along the outersurface of the cavities 61 a, 62 a and support core 66. The wall surfacefacing the recess 64 a is pressed and deformed by internal pressure ofthe pressurized air. Other means of introducing pressurization are wellknown in the art and are within the scope of the present invention.

[0181] As defined herein, the term gas includes air, other gases, andany combination of gases and air. The use of such gases forpressurization is known in the art, the present invention is not limitedto air. Other gases are well within the scope of the invention such asnitrogen gas.

[0182] As a result, the confronting first wall 62 and second wall 63 aredisposed at an interval to provide proper rigidity and impact absorbingqualities. The ribs are orientated in the impact action directionbetween the first wall 62 and second wall 63. The leading ends of theflat rib 26 projecting from first wall 62 to second wall 63 and thehollow rib 27 adjacent to both side ends of the flat rib 26 areintegrated through the fusion portion 71 on the inner surface fromsecond wall 63, thereby completing the impact absorbing rib 30.

[0183] The final step involves cooling in the molds, opening the molds61, 62, removing the hollow article 21, and deflashing. The supportcores, if retractable, can be retracted once the hollow ribs are formed.

[0184] In the manufacturing method of the hollow article according tothe invention, the surface of the slide core retractably disposed in themold may be covered with a coating layer made of fluoroplastic resinwhich makes it easier to slide. The application of the coating layer offluoroplastic resin is improved by roughening the surface of the slidecore and then applying a coating layer of fluoroplastic resin on therough surface.

[0185] The coating layer is not limited to a thin layer of fluoroplasticresin, but can also be formed by co-deposition of fluoroplastic resinand plating solution such as electroless nickel in a treating solution,and applying and baking the treating solution on the surface of theslide core. Alternatively, the coating layer can also be prepared byforming an electroless nickel coating on the surface of the slide core,and impregnating fluoroplastic resin in this electroless nickel coating.

[0186] The hollow article of the present invention, used for example inthe automotive industry, encompasses an impact absorbing rib made offlat rib and hollow rib disposed adjacently to both side ends of theflat rib and is integrally formed between the confronting first wall andsecond wall disposed at an interval in impact action direction. There isan impact absorbing rib uniform in shape, dimensions and wall thicknesson the whole and is integrally formed by blow molding. As a result, ahollow article useful with an excellent impact absorbing performance isobtained.

[0187] The objects and advantages of the invention may be furtherrealized and attained by means of the instrumentalities and combinationsparticularly pointed out in the appended claims. Accordingly, thedrawing and description are to be regarded as illustrative in nature,and not as restrictive.

What is claimed is:
 1. A method of blow molding a hollow article havinga first wall and a second wall confronting across a spacing, with anintegral rib disposed between said first wall and said second wall,comprising the steps of: opening a split mold, wherein said split moldhas a first mold half with a cavity, and a second mold half with acavity, a slide core and a pair of support cores on either side of saidslide core; extruding a parison of molten thermoplastic resin betweensaid split mold; closing said split mold; deforming said parison withsaid sliding core and said pair of support cores and forming a recess,wherein a leading end of said recess is fused to an inner surface of anopposing wall side; retracting said slide core; introducing a pressuresubstance into said parison; inflating said parison along a cavitysurface of said split molds and said support cores and forming saidintegral rib between said first wall and said second wall, wherein saidintegral rib comprises a flat rib and a pair of hollow ribs; and coolingsaid split mold, opening said split mold and removing said hollowarticle.
 2. The method of blow molding a hollow article according toclaim 1, wherein said step of retracting said slide cores issimultaneous with said step of introducing said pressure substance. 3.The method of blow molding a hollow article according to claim 1,wherein said support cores are retractable.
 4. The method of blowmolding a hollow article according to claim 1, further comprising thestep of retracting said support cores after said article has cooled. 5.The method of blow molding a hollow article according to claim 1,wherein said pressurized substance is a gas.
 6. The method of blowmolding a hollow article according to claim 5, wherein said gas ischosen from the group of gasses consisting of nitrogen and air.
 7. Themethod of blow molding a hollow article according to claim 1, furthercomprising, before the step of extruding a parison, the steps of:roughening a surface of said slide core; and coating said surface ofsaid slide core with fluoroplastic resin.
 8. The method of blow moldinga hollow article according to claim 1, further comprising, after thestep of extruding a parison, the step of: maintaining the mold in anopen position.
 9. A method of blow molding a hollow article having afirst wall and a second wall confronting across a spacing, with anintegral rib disposed between said first wall and said second wall,comprising the steps of: opening a split mold, wherein said split moldhas a first mold half with a cavity, a slide core and a pair of supportcores on either side of said slide core, and a second mold half with acavity, a slide core and a pair of support cores on either side of saidslide core; extruding a parison of molten thermoplastic resin betweensaid split mold; closing said split mold; deforming said parison witheach said sliding core and each of said pair of support cores andforming a first recess and a second recess, wherein a leading end ofsaid first recess and a leading end of said second recess are fused;retracting each of said slide cores; introducing a pressure substanceinto said parison; inflating said parison along a cavity surface of saidsplit molds and said support cores and forming said integral rib betweensaid first wall and said second wall, wherein said integral ribcomprises a pair of flat ribs and a pair of hollow ribs; and coolingsaid split mold, opening said split mold and removing said hollowarticle.
 10. The method of blow molding a hollow article according toclaim 9, wherein said step of retracting said slide cores issimultaneous with said step of introducing said pressure substance. 11.The method of blow molding a hollow article according to claim 9,wherein said support cores are retractable.
 12. The method of blowmolding a hollow article according to claim 9, further comprising thestep of retracting said support cores after said article has cooled. 13.The method of blow molding a hollow article according to claim 9,wherein said pressurized substance is a gas.
 14. The method of blowmolding a hollow article according to claim 13, wherein said gas ischosen from the group of gasses consisting of nitrogen and air.
 15. Themethod of blow molding a hollow article according to claim 9, furthercomprising, before the step of extruding a parison, the steps of:roughening a surface of said slide core; and coating said surface ofsaid slide core with fluoroplastic resin.
 16. The method of blow moldinga hollow article according to claim 9, further comprising, after thestep of extruding a parison, the step of: maintaining the mold in anopen position.